This may be what you are looking for:

use strict;
use warnings;

my $heading = '';
my @lines;

while (my $line  = <DATA>)
  {
  chomp $line;
  if ($line =~ /^[1-9]/)
    {#New heading line
    ProcessEntry ($heading, @lines) if length $heading;
    $heading = $line;
    @lines = ();
    }
  else
    {push @lines, $line;}
  }

ProcessEntry ($heading, @lines) if length $heading;
  
sub ProcessEntry
{
my $heading = shift;
my @lines = @_;

print "Heading is: $heading\n";
print "Lines are:\n   " . join "\n   ", @lines;
print "\n\n";
}
[download]

__DATA__
1. This string can be modified using only regexes
-These strings
-Need to be
-put into an
-array
2.Here's another string needs only regexes
-But here are more
-strings which 
-I want arrayed
[download]

Which prints:

Heading is: 1. This string can be modified using only regexes
Lines are:
   -These strings
   -Need to be
   -put into an
   -array

Heading is: 2.Here's another string needs only regexes
Lines are:
   -But here are more
   -strings which 
   -I want arrayed
[download]