Just a tangential word of caution, Andy; quoting (determining interpolation) matters: 
C:>perl -e "my $var = '0x8';if ($var =~ /^[1-9]\d*$/) {print 'num' } e
+lse {print 'not a num';}"
not a num

[download]

But

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

[download]

In reply to Re^3: Question re numbers and strings by ww
in thread Question re numbers and strings by ultranerds

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