warn
Issues a warning message to STDERR without terminating the program.
Prints the argument to STDERR. If the string does not end with a
newline, Perl appends at FILE line LINE.
If $SIG{__WARN__} is set to a code reference, that handler is
called with the warning message as its sole argument instead of
printing to STDERR. The handler runs in void context and its
return value is discarded.
Synopsis
warn "something looks wrong";
warn "problem at $file line $line\n";
warn $object;
Implementation Notes
perl5 (
pp_sys.c:537): mark-based list op. If SP - MARK > 1, joins all args with “” via do_join into TARG. If SP == MARK (no args), uses “”. Single arg: uses TOPs directly. Then mess_sv for location if no trailing \n, write to stderr.