use strict;
use warnings;

my @strings = (
'string that I need to gather the common base from: number 1 and some other junk in it',
'string that I need to gather the common base from: number 2 and some other junk in it',
'string that I need to gather the common base from: number 3 and some other junk in it',
'string that doesnt meet the proper specifications: number 4 and some other junk in it',
'another string that will fail to match: because it doesnt match DUH!',
'this string will fail as well'
);

for(@strings){
    print $1 . $2 . "\n" if (/^(string that I need to gather the common base from:\s)(.*)/);
}