That's what variables were invented for

my $inp;
print "What column do you want ? ";
do {
  $inp= <>;
  chomp($inp); 
} until ($inp=~/^\d+$/ and $inp>=11 and $inp<=19);

foreach (<$bh>) 

{
   my @text=split(/\t/);
   
   $bHash{$text[0]} = $text[$inp];
}
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In this case the user is asked to type in a column number between 11 and 19