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Diffstat (limited to 'pod/perlfunc.pod')
| -rw-r--r-- | pod/perlfunc.pod | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 8ed707970a..92dbc2a135 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -3795,19 +3795,21 @@ digits. See also L</oct>, if all you have is a string. =item undef Undefines the value of EXPR, which must be an lvalue. Use only on a -scalar value, an entire array, an entire hash, or a subroutine name (using -"&"). (Using undef() will probably not do what you expect on most -predefined variables or DBM list values, so don't do that.) Always -returns the undefined value. You can omit the EXPR, in which case -nothing is undefined, but you still get an undefined value that you -could, for instance, return from a subroutine, assign to a variable or -pass as a parameter. Examples: +scalar value, an array (using "@"), a hash (using "%"), a subroutine +(using "&"), or a typeglob (using "*"). (Saying C<undef $hash{$key}> +will probably not do what you expect on most predefined variables or +DBM list values, so don't do that; see L<delete>.) Always returns the +undefined value. You can omit the EXPR, in which case nothing is +undefined, but you still get an undefined value that you could, for +instance, return from a subroutine, assign to a variable or pass as a +parameter. Examples: undef $foo; undef $bar{'blurfl'}; # Compare to: delete $bar{'blurfl'}; undef @ary; undef %hash; undef &mysub; + undef *xyz; # destroys $xyz, @xyz, %xyz, &xyz, etc. return (wantarray ? (undef, $errmsg) : undef) if $they_blew_it; select undef, undef, undef, 0.25; ($a, $b, undef, $c) = &foo; # Ignore third value returned |