C:>perl -e "my $var = '0x8';if ($var =~ /^[1-9]\d*$/) {print 'num' } else {print 'not a num';}"
not a num

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C:>perl -e "my $var = 0x8;if ($var =~ /^[1-9]\d*$/) {print 'num' } else {print 'not a num';}"
num