Perl Program to parse through error log file, extract error message and output to new file

I need to write a perl program where I parse through an error log and output the error messages to a new file. I am having issues with setting up the regex to do this. In the error log, an error code starts with the word "ERROR" and the end of each error message ends with a ". " (period and then a space). I want to find all the errors, count them, and also output the entire error message of each error message to a new file.

I tried this but am having issues:

open(FH,"<$filetoparse");

    $outputfile='./errorlog.txt';
    open(OUTPUT,">$outputfile");
    $errorstart='ERROR';
    $errorend=". ";

    while(<FH>)
    {
    if (FH=~ /^\s*$errorstart/../$errorend/)   
    {
        print OUTPUT "success";
    }   
    else
    {
        print OUTPUT "failed";
    }
    }

}

the $errorstart and $errorend are something I saw online and am not sure if that is the correct way to code it.

Also I know the printing "Success" or "Failure" is not what I said I am looking for, I added that in to help with confirmed that the code works, I haven't tried coding for counting the error messages yet.

before this snippet of code I have a print statement asking the user for the location address of the .txt file they want to parse. I confirmed that particular section of code words properly. Thanks for any help! Let me know if more info is needed!