#!usr/bin/perl/ -w
$outname="";# reset name of outfile
open (OUT, ">temp.out") || die "cannot open: $!";#open a file for output - 
# as the names of the infiles have not been read yet, I assign this a temporary name to be renamed later
#
while(defined($file=glob("*.fa"))){  #loop opens one file ending in .fa after the other. stores the name in $file 
	open (IN, "<$file") || die "cannot open: $!"; #reports error if file cannot be opened 
	#and assigns $file to IN
	@filename_parts=split(/\./,$file); # writes first part of filename into $filename_parts[0]
     	$outname .= "$filename_parts[0]".'.'; ### concatenated $filename_part[0] into new outname ###
	#repeats this for every cycle
	while (defined($line=<IN>)){print OUT $line;} #writes contents of $file line by line into filehandle OUT
} #no more *.fa files in directory
close OUT; #closes filehandle OUT and temp.out
$outname="$outname".'fa.multiple';#adds useful extension to outfile
system ("mv temp.out $outname"); # uses unix command mv (move)to rename temp.out into new $outname