You can get rid of the second conditional. If the regex succeeds, $1 will be set to the captured element. If the regex fails, $1 will be undefined or whatever was in it previously.

my $sss = "M9";
if ($sss =~ m/(\d+)/){
    print "Value Matched on: $1\n";    # prints Value Matched on: 9
}

$sss = "Mm";
if ($sss =~ m/(\d+)/){
    print "Value Matched on: $1\n";    # if statement is not entered
}

print "\$1 holds $1!\n";
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The generally accepted wisdom is to use conditionals exclusively if you're capturing things. You could also add an else clause, undefining $1.