use strict;
use warnings;

my $header = <DATA>;
my %handles;

while ( <DATA> )
{
    my $handle;
    my $key = substr($_,0,13);
   
    # check if file is already open
    if ( $handles{$key} )
    {
        $handle = $handles{$key};
    }
    else
    {
        #if not, open it and store the handle
        my $name = $key;
        $name =~ s/://;
        
        open $handle, ">$name.txt" or die $!;
        print $handle $header;
        $handles{$key} = $handle;
    }
    
    print $handle $_;
}

__DATA__
    Usr1369***12556
06-01-0101:00    1169 <snipped off>
06-01-0101:00    2396 <snipped off>
06-01-0103:12    1169 <snipped off>
06-01-0103:12    2569 <snipped off>
06-01-0301:00    1169 <snipped off>
06-01-0301:00    2396 <snipped off>