Other bugs:

• "'$strIn'" is critically flawed. (What if $strIn contains a quote...)
• $rtnVal and $retVal are never declared.
• Aren't $rtnVal and $retVal suppose to be the same variable?
• You're using == for lexical comparison. Use eq for that.
• use strict; is probably missing
• Unrequired use of a prototype. Prototypes are best avoided, so sub trim($) { ... } should be sub trim { ... }.
• Sounds like you should be using placeholders (e.g. SELECT * FROM table WHERE field = ?) instead of writing your own quoting function.