Difference in regex escaping

[aeberhart]

Input:
"http://example.org/test{par}"

Expression:
$replace($, /{par}/, '')

Output:
java.util.regex.PatternSyntaxException: Illegal repetition near index 1
{par}
^
at java.base/java.util.regex.Pattern.error(Pattern.java:2028)

should be:
"http://example.org/test"

It works as expected, if the expression escapes the curly brackets:
$replace($, /{par}/, '')