#!/usr/bin/perl
use strict;
use warnings;

#SSCCE:
my %mycorpus = (

			text1 => "This is line 1 from text 1
another line here which should be included in the text file with the above line.
This is line 2 from text 1
This is line 3 from text 1",
			
			
            text2 => "This is line 1 from text 2
This is line 2 from text 2
another line here which should be included in the text file with the above line.
This is line 3 from text 2",

);

my $count = 1;
foreach my $filename (sort keys %mycorpus) {
	my $outfile;
	
	open my $fh, '<', \$mycorpus{$filename} or die $!;
	while (<$fh>) {
		chomp;
		if (/^This is/) {
			close $outfile if $outfile;
			my $out = "UserA_$count.txt";
			open $outfile, '>', $out
				or die "could not open '$out' for writing $!";
			$count++;
		}
		print $outfile $_, "\n" if $outfile;
	}
}