use Modern::Perl;

my @filehandle;
my $maxlength = 10;
for ( 1 .. $maxlength  ) {
    open $filehandle[$_], '>', "text$_.txt" or die "Could not open text$_.txt";
}

while (<DATA>) {
    chomp;
    select $filehandle[ length($_) ];
    say $_;
}

__DATA__
ABC
DEFG
HIJ
KL
1234XYZ
G
HI
S
12ER
34TY