my %fh;

##</code><code>##

while(<>) { # the line read is stored into $_
    chomp; # remove line ending character from $_
    ...
}

##</code><code>##

    my( $data, $fh_token ) = split /\s*:\s*/;

##</code><code>##

    if( ! $fh{$fh_token}) {
        open my $fh, '>', "$fh_token.txt"
          or die "Can't write to '$fh_token.txt': $!\n";
        $fh{$fh_token} = $fh; # store filehandle
    }
    my $fh = $fh{$fh_token}; # this is the filehandle to print to

##</code><code>##

    print $fh $data, "\n"; # append a line break. You'd use "\r\n" on windows.

##</code><code>##

my %fh;
while(<>) { # the line read is stored into $_
    chomp; # remove line ending character from $_
    my( $data, $fh_token ) = split /\s*:\s*/;
    if( ! $fh{$fh_token}) {
        open my $fh, '>', "$fh_token.txt"
          or die "Can't write to '$fh_token.txt': $!\n";
        $fh{$fh_token} = $fh; # store filehandle
    }
    my $fh = $fh{$fh_token};
    print $fh $data, "\n"; # append a line break. You'd use "\r\n" on windows.
}