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Perl Programming/Keywords/warn
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Perl wantarray when Keywords
The warn keyword
warn prints the LIST to STDERR. If the last LIST element is not a newline, it appends the same file/line number text as die does. If the output is empty and the variable $@ contains already a value, this is used after appending "\t...caught" to $@. If this variable is empty, the string "Warning: Something's wrong" is used.
If a $SIG{__WARN__} is installed, no message is printed. With the __WARN__ handler, all the warnings can be suppressed.
Syntax
warn LIST
Examples
warn "\$foo is alive and $foo!";
Perl wantarray when Keywords