You could use a negated character class using all but one of your strings to remove those characters using s///: 
my @s = qw/ 1234579 234789 4578 /;

my $common = pop @s;
$common =~ s/[^$_]//g for @s;

print $common; # 47

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update: reworded description of solution. It's still crap, though:(

In reply to Re: Find characters in ALL strings by FunkyMonk
in thread Find characters in ALL strings by Anonymous Monk

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