use strict;
use warnings;

open my $alusFH, q{<}, \ <<EOD or die qq{open: << HEREDOC: $!\n};
chrabc123	blah	blah
chrdef456	burble	blurgh
Duff line to be rejected
chrabc123	rootle	tootle
EOD

my %seen;
my %fileHandles;
my %outputFiles;

while ( <$alusFH> )
{
    if ( m{^(chr[^\t]+)\t} )
    {
        do {
           open $fileHandles{ $1 }, q{>}, \ $outputFiles{ $1 }
              or die qq{open: > scalar ref.: \n};
           } unless $seen{ $1 } ++;
        print { $fileHandles{ $1 } } $_;
    }
    else
    {
        warn qq{Bad line: $_};
    }
}

close $alusFH or die qq{close: << HEREDOC: $!\n};
do {
   close $fileHandles{ $_ }
      or die qq{close: > scalar ref.: \n};
   } for keys %fileHandles;

print qq{$_:\n\n$outputFiles{ $_ }----------\n}
   for sort keys %outputFiles;

##</code><code>##

Bad line: Duff line to be rejected
chrabc123:

chrabc123	blah	blah
chrabc123	rootle	tootle
----------
chrdef456:

chrdef456	burble	blurgh
----------