When writing programs, there is a likelihood to create endless loops. ACL/E is no exception here.
Likely you know that you can use Statement
OPTION MAXI,nnnn
to restrict the total number of statements. After nnnn statements the ACL ends.
But there is also another way to prevent loops. This works by setting parameter "ACL Runaway Limit" in the first panel of SMRT. The default value is 10000 and is the initial value of a counter. That counter is decreased by one for each Statement processed in an ACL which does not require external intervention like ADD, SUB, KEY, SEARCH, BRANCH, TABF. If a statement that requires external intervention is processed - like INPUT, PAUSE, SEND, WINP - that counter is set back to the initial value. Should the counter reach zero the ACL stops with Error message
SCRIPT TERMINATED DUE TO RUNAWAY CONDITION