use strict;
use warnings;

my $str1 = "10";
my $str2 = "2";

print "$str1 lt $str2" if $str1 lt $str2;
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Prints:

10 lt 2
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which may not be what you expect. If you need to be smart about which operator you should use then you may need to use a regular expression first to determine the nature of the two strings. Regexp::Common::number provides a set of expressions for dealing with numbers in various ways that may be of use to you.