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Diffstat (limited to 'pod/perlfunc.pod')
| -rw-r--r-- | pod/perlfunc.pod | 15 |
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diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 7017c8f5df..6b312536b4 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -628,6 +628,21 @@ Examples: See also undef(). +Note: many folks tend to overuse defined(), and then are surprised to +discover that the number 0 and the null string are, in fact, defined +concepts. For example, if you say + + "ab" =~ /a(.*)b/; + +the pattern match succeeds, and $1 is defined, despite the fact that it +matched "nothing". But it didn't really match nothing--rather, it +matched something that happened to be 0 characters long. This is all +very above-board and honest. When a function returns an undefined value, +it's an admission that it couldn't give you an honest answer. So +you should only use defined() when you're questioning the integrity +of what you're trying to do. At other times, a simple comparison to +0 or "" is what you want. + =item delete EXPR Deletes the specified value from its hash array. Returns the deleted |