I would create two more subs altering the content and have them invoke the printer sub -- atleast that's what I do for logging when in need of collapsing structures before logging.

sub doSomethingX {
    my $string = shift;
    $string =~ tr/foo/X/;
    return doSomething($string);
}

sub doSomethingY {
    my $string = shift;
    $string =~ tr/foo/Y/;
    return doSomething($string);
}

sub doSomething {
    my ($var) = shift;
    print $var;
}
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