#!/usr/bin/env perl -w
use strict;
use File::Slurp 'edit_file_lines';
my $inFile = shift;

edit_file_lines { m/\>/ && s/(\S+)\s.*/$1/ } $inFile;
__END__

##</code><code>##

#!/usr/bin/env perl -w
use strict;
use File::Slurp::Tiny qw/ read_lines write_file /;

my ( $inFile, $outFile ) = @ARGV;
my @keep;
foreach my $line ( read_lines($inFile, chomp => 1) ) { 
  push ( @keep, ($line =~ /\>/ ? (split(/\s/, $line))[0] : $line));
}
write_file( $outFile, join("\n", @keep, '') );