Re^4: Perl cheat sheet (dualvars)

[lodin]

in reply to Re^3: Perl cheat sheet
in thread Perl cheat sheet

$! was an unfortunate choice of variable. :-) It's a dualvar so it has different values if treated as a string or as a numerical.

open my $fh, '<', 'this does not exist';
printf "%s (%d)\n", $!, $!;

__END__
No such file or directory (2)

It's better to just create a copy and pass that, if the subroutine doesn't copy the argument.

lodin

[ikegami]

The example was fine. It doesn't make sense for logger to need the dualvar.

• If you wanted to pass the error string to the sub, the caller would use "$!".
• If you wanted to pass the error number to sub, the caller would use 0+$!.
• If the sub needs both an error string and an error number, it would take two arguments.
• If the sub wants to look at $!, it wouldn't take it as an argument.