How do I reduce a variable's length to 20 characters in Perl?

Basically I have some very long variables and need only the first few characters.

I tried using this regex, but it doesn't work.

$va开发者_Python百科r =~ s/(^.{20})?/$1/g;

It doesn't do anything to it.

Any help would be appreciated.

$var = substr($var,0,20);

Note that the simpler:

substr($var,20) = '';

will croak if the string is less than 20 characters.

Or using substitution (assuming 5.10+):

$var =~ s/^.{20}\K.+//s;

Or using unpack:

$var = unpack 'a20', $var;

substr($var, 20) = "";

deletes characters beyond position 20 in $var.

This is the substitution you probably had in mind:

$var =~ s/^(.{20}).*/$1/;