Hey StirFried. The code Riamus2 Posted should work for you.
The problem you have is the code you are using in your perform is activated each time mirc connects to the server
triggering the script each time it connects. Try removing the code from perform and edit this code Riamus2 posted and edit to what you need and place it in your remotes.

Code:
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on *:start: {
server irc.server1.net -j #chan,#chan,#chan
server -m irc.server2.net -j #chan,#chan
server -m irc.server3.net -j #chan

}

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