Lots of ways to do this task. In Perl, the field width stuff is not important. Below is one way. A "match global" regex is used to extract the pairs and then a while loop puts them into a hash.

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my $x = 'a:1:{s:4:"Name";s:5:"sandy";s:5:"sport";s:7:"cricket";}';
my %hash;
my ($key,$value);

my @tokens = $x =~ m/"(.*?)"/g;
$hash{$key}= $value while (($key, $value)= splice(@tokens,0,2));

print Dumper(\%hash);

__END__
prints
$VAR1 = {
          'sport' => 'cricket',
          'Name' => 'sandy'
        };
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