printf "\e[102m Count[$num] = %s\e[m\n\n", persist($num, $dbg);

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You are not using printf correctly. 


    printf "\e[102m Count[%s] = %s\e[m\n\n", $num, persist($num, $dbg)
+;

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The first argument is a FORMAT string and using variable interpolation could introduce an invalid '%' character. 


    my @dbg = ( );
    map { push @dbg, ($res *= $_) } split(//, $num);

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You are not using map correctly: 


    my @dbg = map { $res *= $_ } split(//, $num);

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In reply to Re^2: Multiplication digit persistence by jwkrahn
in thread Multiplication digit persistence by tobyink

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