Hello karthik92,

Welcome to the Monastery. Well it looks the fellow Monk 1nickt provided an answer to your question. Just to include a two more alternative solutions:

#!/usr/bin/perl
use strict;
use warnings;
# use Benchmark qw(:all) ; # WindowsOS
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS

my $str = "       test of white space";

my $results = timethese(100000000,
            { 'regex'  => sub { $str =~ /^\s/ },
                  'substr' => sub { substr($str, 0, 1) eq ' ' },
                  'ord'    => sub { ord($str) == 32 },
            }, 'none');
cmpthese( $results );

__END__

$ perl test.pl
             Rate  regex substr    ord
regex   9225092/s     --   -44%   -87%
substr 16556291/s    79%     --   -77%
ord    73529412/s   697%   344%     --
[download]

I used Benchmark to compare the alternative solutions and the fastest and best option on this case seems to be ord.

Update: Sample of the proposed solution:

my @strs = ("1234  pass  25  30 1",
        "      pass  25  30 2",
        "1965  pass  35  45 1",
        "      pass  35  45 2");

foreach my $sample (@strs) {
    if (ord($sample) == 32) {
    say "Matched: " . $sample;
    }
}

__END__

$ perl test.pl
Matched:       pass  25  30 2
Matched:       pass  35  45 2
[download]

Update2: In case you are wondering about ord it simply reads the first character and returns the numeric value. From the ASCII table 32 decimal is SPACE number 1 (character) would return 49.

Hope this helps, BR.