oneliner to count the number binary digits in this string 1011111

[suvendra123]

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[LanX]

  DB<34> p "1011111" =~ tr/01//
7

[Anonymous Monk]

 $string_len    = length($binary_number);

[LanX]

  DB<45> p "NOPE! 1011111" =~ tr/01//
7
  DB<46> p length "NOPE! 1011111"
13
  DB<47>

> to count the number binary digits

[BillKSmith]

If you know that the string contains only binary digits, use length('1011111'). Use LanX's method if you wish to ignore non-binary characters.

[davido]

Where is your attempt?

[AnomalousMonk]

LanX's use of the tr/// operator (see perlop) is best (simplest, fastest) for simple counting.

For counting in cases of more complex matching, m// (perlop) can be used:

Win8 Strawberry 5.8.9.5 (32)  Sun 03/14/2021 17:12:13
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings

my $s = '1010011 f1e f0o g0e';

my $n =()= $s =~ m{ (?<= [fg]) [01] (?= [oe]) }xmsg;
print "$n [01] in '$s' \n";

^Z
3 [01] in '1010011 f1e f0o g0e'

See goatse (don't ask) for a discussion of the =()= "operator."