After successfully using grep on a variable it prints blank - perl

Question

I am opening a directory that has files that look like the following. Here is one file:
>UVWXY
ABCDEFGHIJKLMNOPQRSTUVWXYZ
>STUVW
ABCDEFGHIJKLMNOPQRSTUVWXYZ
>QRSTU
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Here is a second file:
>EFGHI
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Here is my code:
#!/usr/bin/perl
use warnings;
use strict;
my ($directory) = #ARGV;
my $dir = "$directory";
my #ArrayofFiles = glob "$dir/*";
open(OUT, ">", "/path/to/output.txt") or die $!;
foreach my $file(#ArrayofFiles){
open(my $fastas, $file) or die $!;
my $numberoffastas = grep{/>/}<$fastas>;
#print $numberoffastas, "\n";
while (my $line = <$fastas>){
print $line, "\n";
}
}
Nothing is printed out for $line, but this code correctly counts the number of ">"s that appear in the file when it is opened, evidenced by printing $numberoffastas.
How can I fix this code so that $line = something like:
>EFGHI
or
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Thanks

Answer 1

my $numberoffastas = grep{/>/}<$fastas>;
calls readline on the $fastas filehandle in list context, which consumes all the input on the filehandle. At your subsequent call in while (my $line = <$fastas>), there is no more input on that filehandle to provide, and the while condition fails.
Save the inputs in an array and perform both operations on the array
my #inp = <$fastas>;
my $numberoffastas = grep {/>/} #inp;
...
foreach my $line (#inp) {
...
}
or if you are worried that the files are too large and will give you memory headaches, reopen the file
my $numberoffastas = grep {/>/} <$fastas>;
close $fastas;
open $fastas, $file;
...
while (my $line = <$fastas>) { ... }
or seek to the beginning of the file
open my $fastas, '+<', $file; # +< means random-access mode
my $numberoffastas = grep {/>/} <$fastas>;
...
seek $fastas, 0, 0; # rewind to beginning of file
while (my $line = <$fastas>) { ... }