The most commonly used PSL operator is the "suffix-implication" operator (a.k.a the "triggers" operator), which is denoted by <math> \mapstotexttt{|=>} </math>. Its left operand is a PSL regular expression and its right operand is any PSL formula (be it in LTL style or regular expression style). The semantics of <math>\texttt{r \mapsto |=>p}</math> is that on every time point i such that the sequence of time points up to i constitute a match to the regular expression r, the path from i+1 should satisfy the property p. There is also a non-overlapping version, which requires p to hold from time i+1 rather than i. This is exemplified in the figures on the right.
[[File:The trigger operator - slide 2.jpg|thumb|path satisfying ''r triggers p'' in two non-overlapping ways]]
[[File:The trigger operator - slide 3.jpg|thumb|path satisfying ''r triggers p'' in two overlapping ways]]
[[File:The trigger operator - slide 4.jpg|thumb|path satisfying ''r triggers p' in three ways]]
The regular expressions of PSL have the common operators for concatenation (<math> \texttt{{color|red|;}} </math>), Kleene-closure (<math> \texttt{{color|red|*}} </math>), and union (<math> \texttt{{color|red|{{code|{{!}}}}}}</math>), as well as operator for fusion (<math> \texttt{{color|red|:}}</math>), intersection (<math> \texttt{{color|red|\&\&}}</math>) and a weaker version (<math> \texttt{{color|red|\&}}</math>), and many variations for consecutive counting <math> \texttt{{color|red|[*n]}} </math> and in-consecutive counting, e.g. <math> \texttt{[=n]} </math> and <math> \texttt{color|red|[->n]}} </math>.
The trigger operator comes in several variations, shown in the table below.
