A bit cryptic, but without the need of $1: 
my $str   = '000001';
my $index = length(($str =~ /^(0*)/)[0]);

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لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: index using a range by choroba
in thread index using a range by romano

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