diff options
Diffstat (limited to 'pod/perlop.pod')
| -rw-r--r-- | pod/perlop.pod | 39 |
1 files changed, 20 insertions, 19 deletions
diff --git a/pod/perlop.pod b/pod/perlop.pod index 5a85e7f648..a485781e40 100644 --- a/pod/perlop.pod +++ b/pod/perlop.pod @@ -620,9 +620,9 @@ the same character fore and aft, but the 4 sorts of brackets "" qq{} Literal yes `` qx{} Command yes (unless '' is delimiter) qw{} Word list no - // m{} Pattern match yes - qr{} Pattern yes - s{}{} Substitution yes + // m{} Pattern match yes (unless '' is delimiter) + qr{} Pattern yes (unless '' is delimiter) + s{}{} Substitution yes (unless '' is delimiter) tr{}{} Transliteration no (but see below) Note that there can be whitespace between the operator and the quoting @@ -753,22 +753,22 @@ Options are: If "/" is the delimiter then the initial C<m> is optional. With the C<m> you can use any pair of non-alphanumeric, non-whitespace characters -as delimiters (if single quotes are used, no interpretation is done -on the replacement string. Unlike Perl 4, Perl 5 treats backticks as normal -delimiters; the replacement text is not evaluated as a command). -This is particularly useful for matching Unix path names -that contain "/", to avoid LTS (leaning toothpick syndrome). If "?" is +as delimiters. This is particularly useful for matching Unix path names +that contain "/", to avoid LTS (leaning toothpick syndrome). If "?" is the delimiter, then the match-only-once rule of C<?PATTERN?> applies. +If "'" is the delimiter, no variable interpolation is performed on the +PATTERN. PATTERN may contain variables, which will be interpolated (and the -pattern recompiled) every time the pattern search is evaluated. (Note -that C<$)> and C<$|> might not be interpolated because they look like -end-of-string tests.) If you want such a pattern to be compiled only -once, add a C</o> after the trailing delimiter. This avoids expensive -run-time recompilations, and is useful when the value you are -interpolating won't change over the life of the script. However, mentioning -C</o> constitutes a promise that you won't change the variables in the pattern. -If you change them, Perl won't even notice. +pattern recompiled) every time the pattern search is evaluated, except +for when the delimiter is a single quote. (Note that C<$)> and C<$|> +might not be interpolated because they look like end-of-string tests.) +If you want such a pattern to be compiled only once, add a C</o> after +the trailing delimiter. This avoids expensive run-time recompilations, +and is useful when the value you are interpolating won't change over +the life of the script. However, mentioning C</o> constitutes a promise +that you won't change the variables in the pattern. If you change them, +Perl won't even notice. If the PATTERN evaluates to the empty string, the last I<successfully> matched regular expression is used instead. @@ -911,8 +911,9 @@ A double-quoted, interpolated string. =item qr/STRING/imosx Quote-as-a-regular-expression operator. I<STRING> is interpolated the -same way as I<PATTERN> in C<m/PATTERN/>. Returns a Perl value which -may be used instead of the corresponding C</STRING/imosx> expression. +same way as I<PATTERN> in C<m/PATTERN/>. If "'" is used as the +delimiter, no variable interpolation is done. Returns a Perl value +which may be used instead of the corresponding C</STRING/imosx> expression. For example, @@ -1072,7 +1073,7 @@ variable is searched and modified. (The string specified with C<=~> must be scalar variable, an array element, a hash element, or an assignment to one of those, i.e., an lvalue.) -If the delimiter chosen is single quote, no variable interpolation is +If the delimiter chosen is a single quote, no variable interpolation is done on either the PATTERN or the REPLACEMENT. Otherwise, if the PATTERN contains a $ that looks like a variable rather than an end-of-string test, the variable will be interpolated into the pattern |