The postfix if (! $line=~m/^\s*exit\s*$/i) is not doing what you expected.

#!/usr/bin/env perl
use strict;
my $line = 'not an exit statment';
print "line matched ! =~\n"      if (! $line =~ m/^\s*exit\s*$/i   );
print "line matched !(=~)\n"     if (! ($line =~ m/^\s*exit\s*$/i) );
print "line matched not =~ \n"   if (not $line =~ m/^\s*exit\s*$/i );
print "line matched if !~\n"     if ( $line !~ m/^\s*exit\s*$/i );
print "line matched unless =~\n" unless ($line =~ m/^\s*exit\s*$/i);
__END__
line matched !(=~)
line matched not =~
line matched if !~
line matched unless =~
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The ! operator has a much higher precedence than the not operator does. Using parentheses with the ! applies it to the result of the match; not with its lower precedence does so by default.

When $exp->send sends the exit command to isql, isql disconnects and Expect.pm notices and handles that. If you are writing a production-quality program - especially one that will run automatically - you'll want to code your own checks for errors, disconnects, etc. OTOH, if this is for your own use only, run manually to simply automate a task, then you can usually get away with letting the Expect module handle anomalies. (I assume you're backing up whatever DB objects are being modified prior to letting a program make changes...)