$ echo "F001            1.2
F101            3.2
solvent1      0
solvent2     3

F001            2.2
F101            7.2
solvent1      5
solvent2     0
" | perl -e'
$/ = "";
while ( <> ) {
    my %x = split;
    my ( $key ) = grep $x{ $_ } eq "0", keys %x;
    for ( sort keys %x ) {
        next if $x{ $_ } eq int $x{ $_ };
        print "${key}_$_ => $x{$_}\n";
        }
    }
'
solvent1_F001 => 1.2
solvent1_F101 => 3.2
solvent2_F001 => 2.2
solvent2_F101 => 7.2