Shell Programming and Scripting

perl -ne'
  /^(\w+)\s*=\s*$/ and 
    $stmt .= "conn username/pass\@$1\n\@checkinstance.sql\n";
  if (eof) {
    ($cmd = <<_END_) =~ s/^\s+//gm;
      sqlplus /nolog<<_SQL_
        $stmt
      _SQL_
_END_
    qx/$cmd/;
       }' tnsnames.ora

perl -lne'
  /^(\w+)\s*=\s*$/ and 
    print "conn username/pass\@$1\n\@checkinstance.sql\ndisc"
  ' tnsnames.ora

while read svc; do
  svc="$(
    expr "$svc" : '^\([a-zA-Z_]*\) *= *$' 2>/dev/null
    )" && 
    printf 'conn user/pass@%s\n@checkinstance.sql\ndisc\n' "$svc"
done<tnsnames.ora