okay, AnomalousMonk, this works: 
# the original number of integers to test (will be one-upped)
my $i = 1; 

# the input string to be tested (a number)
my $foo = shift;

# see if the input string is a two-digit number
my $rc = ($foo =~ m{ \b (??{ ++$i; qr{\d{$i}}; }) \b }xmsg) ?'Y' :'N';

[download]
very clever...thanks.

In reply to Re^3: Calculating variable {n} in regex match by atreyu
in thread Calculating variable {n} in regex match by atreyu

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