>>72 Perl5

for $a (qw{090 0080 123 0 000}) {
 ($b = $a) =~ s/^0*([\d])/$1/;
 print "$a → $b\n"
}

実行結果
~ $ perl 17_72_0dec.pl
090 → 90
0080 → 80
123 → 123
0 → 0
000 → 0