#! /usr/local/bin/perl -w
use Regexp::Assemble;
my $ra = Regexp::Assemble->new->add(
    'Error 124 on User1:FileA no space left', 
    'Error 124 on User2:FileB no space left', 
    'Error 124 on User3:FileC no space left'
);
print $ra->re;