use strict;
use warnings;

my $fileStr = <<STR;
F001            1.2
F101            3.2
solvent1      0
solvent2     3

F001            2.2
F101            7.2
solvent1      5
solvent2     0
STR

open my $fIn, '<', $fileStr or die "Couldn't open \$fileStr: $!\n";